Comprehensive Study on Graphene Nanofluids and its Applications: Literature Review


Dave Archit1*, Dr. Sharma Kuldeep2, Dr. Chandramuly R. Sharma3

1Assistant Professor, Parul Institute of Applied Sciences and Research (PIASR), Parul University,

P.O. Ghuma, Bopal - Ghuma Road, Ahmedabad, Gujarat - 380058.

2Director, Parul Institute of Applied Sciences and Research (PIASR), Parul University,

P.O. Ghuma, Bopal - Ghuma Road, Ahmedabad, Gujarat - 380058.

3Assistant Professor & HOD, Chemistry Department, LJIAS, LJ University, Ahmedabad Gujarat

*Corresponding Author E-mail:,



In this review, the heat transfer capabilities of graphene nano fluids have been explored theoretically and experimentally. This review embraces the experimental results about the capabilities of graphene nano fluids along with heat transfer performance and recaps the recent growth on preparation and evaluation methods, the ways to enhance the stability of graphene nano fluids and future applications in various fields of energy. Moreover, this review paper also specifies the inconsistencies among them. Further, this critical review helps the researchers to investigate the heat transfer on graphene nanofluids embedded with conducting dust particles.


KEYWORDS: Thermal Conductivity, Nanofluids, Nano particles, graphene nanoparticles.




Nowadays, the industrial technology developments are mainly focussing on the optimization of energy and in reducing the processing time of a system. As a result, the ultra-high performance in cooling and heating of the thermal systems become an essential in the heat transfer field. In several engineering applications, heat transfer along a fluid medium is significant in automobiles, heat exchangers, refrigerators and power plants. Heat transfer through a fluid medium is important in several engineering applications, including heat exchangers, refrigerators, automobiles and power plants. The capacity of a fluid medium to transfer a huge quantity of heat over a small temperature difference increases the effectiveness of energy conversion and upgrades the design and performance of automobile engines, heat transfer devices and micro-electro-mechanical systems (MEMS). Heat transfer through fluid is basically convection control. However, the thermal conductivity of the fluid strongly depends on the coefficient of convective heat transfer1


Thermal conductivity can be improved by suspending solid particles in the liquid medium is an effective approach as thermal conductivity of solids is greater than that of fluids. A nano fluid is a new class of solid liquid mixtures of stable colloidal suspension of nanometre size particles i.e., multivalued carbon nanotubes which enhances the conductivity of the fluid. Nano fluids are the most potential heat transfer fluid used as a coolant. Nanofluid is not only the mixture of liquid-solid alloys. It is also having some special characteristics like stable suspension, durability and collection of particles. Due to the fascinating thermal characteristics of nanofluids, this research has attracted a vast interest from the researchers worldwide2


Nanofluids are the suspensions of the nano meter sized metallic or non-metallic powders into base fluids. Convectional base fluids contain mm or micro meter sized particles. Due to this reason, the thermal conductivity of the convectional base fluids has inherently poor while compared with the solids. The suspension of nano powders into convectional base fluids helps to enhance the heat transfer rate.3


Nanofluids can be produced in various methods. Mainly they are of two types: 1) One-step and 2) Two step methods. Preparation of nanofluid by one-step method, both the preparation of nano particle and production of affects are made out simultaneously in a collective process. This method has a few advantages like minimizing the agglomeration of nano particle. But some production methods are costly and troublesome. The most commonly used method is the two-step method, nano particles, nanotubes, nanofibers or any nanostructured materials are primarily symphonized as dry powders by physical or chemical methods. Then the dry powders are distributed in the conventional base fluids. Conversely, because of high surface activity of particles, agglomeration/aggregation of nano particles is inevitable. Consequently sedimentation of nano particles can happen in these methods, which influence the nanofluid properties negatively. This is the disadvantage in the two-step method.4


From the previous literature, nano particles could be metallic, non-metallic compounds as Ag, Cu, Ni, Au, Fe, etc., ceramic compounds such as oxides (Al2O3, Fe3O4, ZnO, SiO2, Fe2O3, CuO, TiO2, CeO2,) sulfides (WS2, MoS2) and carbides (SiC). Nano particles can be also carbon based compounds, like carbon nanotube, graphene, graphene oxide, graphite and also nanoscale liquid droplets. Base fluids are certain from water, ethylene glycol, mixture of water and ethylene glycol, diethylene glycol, polyethylene glycol, engine oil, vegetable oil, paraffin, coconut oil, gear oil, kerosene, pump oil, etc.5-9


Thermal conductivity denotes the ability of heat transfer and is most important in thermal applications. Thermal conductivity ratios, defined as thermal conductivity of the nanofluid (knf) divided by the thermal conductivity of the base fluid (kf). By using the carbon based nano structures in nanofluids, the heat transfer coefficient may be increased. One author analyzed the heat transfer characteristics of the nanofluid by considering the different types of nano fluids and found a large improvement in effective thermal conductivity of the fluids containing metallic nano particles.10


Stability of Nanofluids:

Preparation of a stable homogeneous nanofluid is a great challenge. Between the nanoparticles repulsive and attractive forces exist. For stable nanofluids the repulsive force must be more than the attractive forces. In general, there are three different techniques utilized by researchers to improve dispersion behaviour of nanofluids and to minimize particles aggregation which acts against long-term stability. However, clustering and aggregation have been reported as features increasing thermal conductivity of nanofluids. Therefore, in preparation, both issues should be taken into account to make a balance between stability and thermal conductivity of a nanofluid. Some methods were recommended for obtaining stable nanofluids, including physical or chemical consideration (i.e. Addition of surfactant, pH control, Ultrasonic agitation (vibration), etc.). Nanofluid stability is directly proportional to its electro-kinetic properties. Thus, control of pH can enhance the stability because of strong repulsive forces.11


Factors influencing on stability of nanofluids:

To attain a stable nanofluid the major role plays by surfactants, pH adjustment, nanofluid preparation method, mixing/homogenization and nano particles. To get a stable fluid both physical and chemical methods are applied.


Surface modifiers:

The sedimentation of nano particles can be avoided by adding proper surface modifiers which are nothing but molecules like zwitterionic or polymers. In general, the stability of the fluids can be increased by adding surfactants, which contains a hydrophobic tail portion, usually a long-chain hydrocarbon, and a hydrophilic polar head group. Surfactants used in nanofluids are also called dispersants. Adding dispersants in the two-phase systems is an easy and economic method to enhance the stability of nanofluids. Moreover, surfactant molecules attaching on the surfaces of nanoparticles may increase the thermal resistance between the nanoparticles and the base fluid, which may bound the improvement of the effective thermal conductivity.12


Solution ph:

Nano particle produce an electric field by applying a surface charge which follows attraction or repulsion of nano particles. The ph value of the fluid mainly depends on the charge. There should be a lot of difference between the values of ph and the isoelectric Point (IEP) of the particles, so that the total charge on the nanoparticles becomes zero. Precipitation occurs when the values of pH and the IEP of the suspension comes close, because of weak repulsive forces among them.


Fabrication method:

As referred before, by using a one-step method for the preparation of nanofluids, in which both nanoparticle manufacturing and nanofluid fabrication are executed simultaneously by avoiding the different phases like storage, dispersion of nanoparticle, drying and transportation. By this we can get a solution with minimum quantity of NPs agglomeration, which at last may increase the stability of nanoparticle.


Concentration of NP:

If the concentration of the solution is very high, the nano particles try to form agglomerations in the suspended solution. For this reason, the control on the concentration of nanoparticle is very important for a better stability.


Mixing methods:

There are different mixing methods like, ultrasonic bath, homogenizer and processor in which the nanostructured particles scattered very well in the base fluid. In recent times, many researchers used ultrasonic disruptor apparatus which is more accessible for mixing. The methods discussed above will help to get a stable nanofluid.



The graphane is intentional material at the present which is a single atomic layer of graphite and has two-dimensional form of carbon. It is a hexagonally pattern lattice made of carbon atoms. These are known as the σbonds placed towards the neighbouring atoms. These covalent carbon-carbon bonds are nearly alike to the bonds holding diamond together giving graphene similar mechanical and thermal properties as diamond. The carbon-carbon bond length in graphene is about 0.142 nanometres. Graphene sheets heap to form graphite. One heap of 3 million sheets = 1 millimetre thick. Graphene is the basic structural element of some carbon allotropes such as (a) Graphite (b) Charcoal (c) Carbon Nanotubes and (d) Fullerence. It is considered as semi-metal because the band gap is zero.13


The main advantages of graphene nanoparticles are:

1    Easy to synthesis and longer suspension time (More stable)

2    Larger surface area/volume ratio (1000 times larger)

3    Higher thermal conductivity

4    Lower erosion, corrosion and clogging

5    Lower demand for pumping power

6    Reduction in inventory of heat transfer fluid

7    Significant energy saving


Preparation of graphene and graphene based nanofluids:

Preparation of Base Fluid:

Generally, in all heat exchangers water is the main heat transfer medium for the reason that it has excellent thermo physical properties and also its availability. To lower the freezing point of water below 4°C we add another liquid to it. The most popular anti freezing agent is Ethyl glycol. To get one liter of base fluid, 700ml water and 300ml ethylene glycol is stirred well and used.


Preparation of Graphene Nanofluid:

The production process can be divided into chemical vapour deposition (CVD), exfoliation, doping and reduction of grapheme oxide. Graphene preparation can be done in various methods such as Solvothermal synthesis, micromechanical cleavage and chemical vapour deposition. To produce it in bulk, the better method is chemical one. One author introduced a chemical method by which we can prepare Graphene water nanofluid. For this first graphene oxide was prepared and then minimized to make Graphene nanoparticles. Distilled water was used as the base fluid. Graphene oxide was synthesized by Hummer's method.14


Another author introduced a method for preparing nanofluid containing graphene oxide Nano sheets and experimentally found that the thermal conductivity of Graphene oxide nanofluid increases 30.2%, 62.3% and 76.8% for 5 Vol% graphene oxide Nano sheets in water, propyl glycol and liquid paraffin respectively. Nanofluid was obtained by exfoliation of graphene oxide in anhydrous ethanol. Another author presented a method to prepare the metal oxide decorated graphene dispersed nanofluids. Another author prepared highly stable graphene based nanofluids by dispersing grapheme oxide powder into the DW with help of ultra-sonication and adding hydrazine hydrate into the mixture. Another author introduced a method to prepare the solvent-free graphene nanofluid. They have synthesized the Graphene oxide with modified Hummers’ method and then with help of ammonia solution (pH = 10) under sonication and ionic surface modifier, the khaki precipitate was formed. Then, the precipitate was washed with deionized water and methanol to remove the excess of ionic surface modifier and dried in the oven. The prepared Graphene nanofluid has a range of 8.5 < pH < 10.5.15 Another author reported the effect of temperature on thermal conductivity first for nanofluids based on metal oxide. As temperature increased from 21°C to 51°C, they observed 2 to 4 fold increase in thermal conductivity.15


Properties of graphene nanofluids:

Graphene nanofluids have special properties which has many applications in engineering.


They are:

1    Thermal conductivity can be enhanced.

2    Heat transfer ability can be increased.

3    Improves the stability over other nanoparticles

4    Better lubrication due to the unique structure

5    Erosion, corrosion and clogging in systems can be reduced.



The available literature on nanofluid was overviewed in this present paper. By this we know that the nanofluids are having the great importance in heat transfer processes. And we come across the various methods for the preparation of nanofluids and the different applications of nanofluids, the evaluation methods for their stability, the ways to enhance their stability, and so forth. Thermal conductivity was found to be enhanced with the increase in particle volume fraction of nanoparticles. Investigation of the thermal performance of nanofluids at high temperatures may widen the possible application areas of nanofluids. The second part of the review is about the graphene nanofluid, its preparation and also applications. Nanoparticle concentration; size; shape; base fluid; temperature; additives and acidity exert influence on the thermal conductivity of graphene nanofluid.16


The following are the conclusions got from the published literature:

1    In general nanofluid thermal conductivity increases linearly with nanoparticle concentration.

2    Enhancement of Thermal conductivity of nanofluids is independent of temperature.

3    Thermal conductivity was influenced by Clustering.


Based on the literature study, researchers have given more attention on the graphene based nanofluids than other fluids. We conclude that the graphene is a silent capable material to be used as heat exchanging fluid. However, the research in this area is still new and more attention require for graphene nanofluids. Our industry and technology have a strong need for the better fluids which can transfer heat more efficiently. Heat transfer by the nanofluids is more proficient than the conventional base fluids. But there is a discrepancy due to the clustering of nanoparticles. The intensity of clustering mainly depends on the pH value and the additives used. Hence the researchers should give complete information about the additives utilized and pH values of the samples.17


The authors have concentrated more on nanofluids, but only a few researchers worked on hybrid graphene nanofluids. Therefore, researchers must give focus on the combinations of different types of nanoparticles (i.e., hybrid nanofluid) and verdict out the main parameters which affect the thermos physical properties of graphene nanofluids. Different combination of salt and hydrogen bond donors to synthesize better Deep eutectic solvents for the applications in increasing heat transfer processes especially in heat exchanger must be examined. Graphene based engine oil nanofluids have to be prepared and their frictional characteristics (FC), antiwear (AW), and extreme pressure (EP) properties have been evaluated. Exploration of non-aqueous nanofluids such as refrigerants which present higher graphene nanofluid stability is also necessary.18-21



We acknowledge for all the helping hands who helped to conduct this study.



The authors declare that they have no conflict of interest.



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Received on 01.01.2021       Modified on 24.05.2021

Accepted on 08.07.2021      ©A and V Publications All right reserved

Research J. Science and Tech. 2021; 13(3):200-204.

DOI: 10.52711/2349-2988.2021.00030